be2iscsi: Fix bogus WARN_ON length check

be2iscsi: Fix bogus WARN_ON length check

drivers/scsi/be2iscsi/be_main.c: In function 'be_sgl_create_contiguous':
drivers/scsi/be2iscsi/be_main.c:3187:18: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
  WARN_ON(!length > 0);

gcc version 5.2.1

Signed-off-by: Tim Gardner <[email protected]>
Cc: Jayamohan Kallickal <[email protected]>
Cc: Minh Tran <[email protected]>
Cc: John Soni Jose <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Reported-by: Joel Stanley <[email protected]>
Reviewed-by: Manoj Kumar <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>